COLUMN ONE : American Culture on a Bun : At 25, the Big Mac is an icon of high cholesterol and lowbrow fare. Its strongest selling point, many believe, is not its decadence or power to satisfy, but its steadfast, if squishy, sameness.

The sandwich, dubbed the Bob's Big Boy, was an instant hit. Word of the unusually built burger and its pudgy-cheeked, overall-clad mascot spread quickly. Soon, according to Tennyson, the hamburger expert, "double-decker burgers were as common as bunk beds at summer camp, and rotund little 'Burger Boy' mascots were everywhere, as Big Boy begat Chubby Boy, Hi-Boy, Bun Boy, Beefy Boy, Country Boy, Brawny Boy, Husky Boy, Yumi Boy, Lucky Boy, Super Boy and several hundred other variations on the theme."

But the descendant that would outshine them all would not make his appearance until the 1960s--three decades after the Big Boy's birth. Jim Delligatti, a onetime Southern Californian operating McDonald's restaurants in Pittsburgh, Pa., wanted to broaden his customer base by offering larger, adult fare. The double-decker leaped to mind.

"This wasn't like discovering the light bulb," Delligatti said. "The bulb was already there. All I did was screw it in the socket."

Convincing McDonald's higher-ups that he should be allowed to diversify was not easy. Back then, the McDonald's menu was brief, one veteran grillman said: "Hamburger, cheeseburger, double cheese, french fries, milkshakes, Coke, orange and root beer, with grilled cheese on Friday for the Catholics." Conventional wisdom cautioned against moving beyond the basics. But Delligatti kept pushing.

It took two years to get permission, and even then, there were limits. According to John F. Love's 1986 book, "McDonald's Behind the Arches," McDonald's decreed that the Big Mac would be tested at one store and be built with a standard bun. Delligatti ignored the latter caveat, ordering an oversize sesame seed bun, cut in thirds.

Within a few months, the Big Mac had boosted sales in Delligatti's store by 12%. Within a year, in 1968, McDonald's added the so-called "seven-course meal" to the menu in all its stores and marketed it with the biggest national advertising campaign it had mounted up to that time.

The success of the Big Mac, which initially cost 49 cents, started a spate of experiments that further expanded McDonald's menu. Soon, inventive franchisees had created the Hot Apple Pie in Knoxville, Tenn., the Egg McMuffin in Santa Barbara, and the Filet-o-Fish in Cincinnati.

Scott Allmendinger, editor of Restaurant Business magazine, says the Big Mac changed the fast-food industry forever. In its wake, simple fare was simply no longer enough.

"When you see a Monterey Chicken Sandwich at Wendy's, this is really where it started," he said. The Big Mac "proved that tinkering with the basic formula could have a true business payoff. (It's) the forefather of menu diversification."

Even the best new product, however, was nothing without one essential ingredient: promotion. Orenstein, the ad man, remembers being summoned in 1969 to create a powerful ad campaign celebrating the Big Mac's first birthday. Even then, he says, the burger was marketed as an American institution.

He and his colleagues at D'Arcy Advertising created an ad featuring singer Hoyt Axton climbing a mountain as he strummed his guitar and sang "The Ballad of Big Mac." "When McDonald's gave the news one beautiful morn, ev'ry hamburger fan had a thrill," Axton crooned, as a mountain-size Big Mac came into view. "Said a new kind of hamburger's about to be born--now will it be a boy or a grill?"

Such ads did their job. And as sales mounted, McDonald's was quick to turn those numbers into larger-than-life visual images--a gimmick still in use. According to McDonald's, for example, if you took all the Big Macs ever sold and stacked them on top of each other, they would stretch to the moon and back two times, circle the Earth 35.5 times or span 589 lengths of the Great Wall of China.

But the two ad campaigns that would forever cement the Big Mac in the American psyche came in the late 1970s. One grew out of McDonald's belief that Big Mac commercials should talk about what the sandwich was made of--an idea that, on its face, seemed a sure-fire recipe for boredom. Then, two ad-men tried turning the seven ingredients into a single word.

The result, the "twoallbeefpatties - specialsaucelettucecheesepicklesonions - onasesameseedbun" campaign, featured real customers attempting to recite the tongue-twister. The rapid-fire jingle, which was soon being repeated on schoolyards across the nation, did more than sell burgers. It became part of the landscape, what one scholar calls folk art.

Then came the "Big Mac Attack," a campaign beginning in 1977 that warned of a super-powered craving that could strike anyone at any time.